Industrial Technology Research Institute

Yunn-Hwa Wang

Tien-Yu Wu

Yung-Peng Hwung

In an autozero type MOSFET comparator, the spurious current induced by the high frequency input voltage can flow through the resistance of the reset switch to introduce an offset voltage error during the autozero mode. A canceler is used to prevent the spurious current from flowing through the reset switch. A T-network with two series capacitors and a shunt switch is used as the canceler. The spurious current is by-passed by the shunt switch and prevented from flowing through the reset switch placed at the output of the T-network. The spurious current canceler is particularly useful for a sub-ranging ADC, where the comparator is used also as a sample-and-hold circuit to hold the input voltage across the series capacitors by opening all the sampling switches, the reset switch and the shunt switch.

Input voltage-induced spurious current canceler for autozero type

A timing control for precharged digital circuits to avoid spurious error appearing at the output due to the slow pull-down of the precharged node after precharging. A NAND gate is used to delay the precharged node siganl transmitting to the output stage until the precharged node is fully discharged. This timing control circuit is used to prevent any spurious peaking of the output of an analog-to-digital converter using precharged bit lines.

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Taipei, Taiwan

Yunn-Hwa Wang